Power electronic modules are semiconductor packages that are used in power electronic circuits. Power electronic modules are typically used in vehicular and industrial applications, such as inverters and rectifiers. The semiconductor components included in the power electronic modules are typically an insulated gate bipolar transistor (IGBT) or a metal-oxide semiconductor field effect transistor (MOSFET) implemented on a semiconductor die. The IGBT and MOSFET semiconductor die may have varying voltage and current ratings. Some power electronic modules also include additional semiconductor circuits (i.e. free-wheeling diodes) in the semiconductor die for overvoltage protection. Additionally, power electronic modules may further include some logical functionality in a semiconductor die.
In general, two different power electronic module designs are used. One design allows the power electronic module to be integrated in a surface mount device (SMD) package for mounting on a printed circuit board (PCB). A second design enables the power electronic module to combine multiple semiconductor dies for realizing a more complex integrated power electronic circuit.
An exemplary SMD package for mounting a power electronic module is shown in FIG. 7. In particular, FIG. 7 illustrates a top view of an exemplary power electronic module 200 with package 230 according to an exemplary embodiment of the related art.
As can be seen from FIG. 7, the SMD package 230 is formed in a parallelepiped shape, for example, out of plastic or ceramic. At a left and a right side, the package 230 provides a recess 245 enabling a secure mounting of the package 230 to a heat sink or to a printed circuit board (PCB). For electrically connecting a semiconductor die housed in the package 230, three leads 210-220 are provided on one side of the package. Each end portion of leads 210-220 forms a terminal for soldering the power electronic module 200 to a contact point of a PCB. Since FIG. 7 illustrates the top view of the package, only the external portions of leads 210-220 are shown.
Further, on the side of the package 230 opposite to leads 210-220, base plate 225 is shown. Base plate 225 is commonly used for mounting a semiconductor die. Additionally, base plate 225 provides mechanical support for the package 230. Further, a label 240 is provided on the front surface of package 230 in order to identify the housed power electronic module.
A further exemplary SMD package for mounting a power electronic module is shown in FIG. 8. In particular, FIG. 8 illustrates a side view of the exemplary power electronic module 200 with package 230 as shown in FIG. 7.
As can be seen from FIG. 8, the overall dimension of the SMD package 230 mounting the power electronic module is primarily determined by the size of the package 230. The thickness of package 230 mainly results from the thickness of the base plate 225 and the area for connecting the leads to the semiconductor die which will be further explained with respect to the exemplary embodiment shown in FIG. 10. In order to structurally attach leads 210-220 within package 230, the internal portion of each lead should be solidly rooted in package 230. The area of package 230 necessary for firmly fixing the leads to the package also adds to overall the size of package 230, which will be further explained with respect to the exemplary embodiment shown in FIG. 9.
In order to enable mounting package 230 at the back surface onto a PCB, the leads 210-220 are bent such that the end portion of each terminal is in the plane defined by the back surface of the package 230. In particular, the leads 210-220 are bent twice; firstly leads 210-220 are bent at a point close to the package exit point in a direction towards the back surface of package 230, and secondly leads 210-220 are bent at a point close to the end portion of leads 210-220 such that the end portion of leads 210-220 is in a same plane as that defined by the back surface of package 230.
On the side of package 230 opposite to leads 210-220, base plate 225 is shown to protrude from the package boundaries.
A further exemplary SMD package for mounting a power electronic module is shown in FIG. 9. In particular, FIG. 9 illustrates a cross-sectional top view of the exemplary power electronic module 200 with package 230 as shown in FIG. 7 and in FIG. 8.
As can be seen from FIG. 9, the package includes a semiconductor die 205, a main portion of base plate 225 and bond wires 235. In particular, the back surface of semiconductor die 205 is bonded to the base plate 225. The front plane of semiconductor die 205 provides structures for connecting wire bonds 235. In particular, the wire bonds 235 electrically connect the semiconductor chip 205 to the leads 210-220. Lead 210 is connected to the semiconductor die 205 via one wire bond 235. Lead 220 is connected to semiconductor die 205 via two parallel wire bonds 235. Lead 210 is connected to the back surface of the semiconductor die 205.
For a structurally secure attachment of leads 210-220 with package 230, the internal portion of leads 210-220 is shaped as an anchor with a hole at a center of the anchor head. In particular, molding the package the anchor shape of the internal portion of the leads 210-220 allows for a structurally firm attachment of leads 210-220 within the package 230.
Further, base plate 225 is formed to protrude from the package 230 at the side of the package 230 opposite to the leads. The illustrated exemplary power electronic module 200 is 10.18 mm wide and 15.55 mm long.
As can be seen from the exemplary SMD package illustrated in FIG. 9, the length of the package is mainly determined by the size of the semiconductor die 205 and the internal portions of the leads 210-220 necessary for firmly attaching the leads 210-220 within the package 230.
Another exemplary SMD package for mounting a power electronic module is shown in FIG. 10. In particular, FIG. 10 illustrates a cross-sectional side view of the exemplary power electronic module 200 with package 230 shown in FIG. 7, FIG. 8 and in FIG. 9.
In the package 230 of the power electronic module, the semiconductor die 205 is bonded at the back surface with the base plate 225. On the top surface of the semiconductor die 205, the wire bonds 235 are attached. As the internal portions of the leads 210-220 are not allowed to overlap the semiconductor die 205 or the base plate 225, the bond wires provide an electric connection between the semiconductor die 205 and the leads 210-220.
In particular, the package 230 shown in FIG. 10 provides a distance between the semiconductor die 205 and leads 210-220. By displacing the internal portions of the leads 210-220 in a vertical direction, the direction opposite to the back surface of the package 230, the horizontal distance between the leads 210-220 and the semiconductor die 205 can be maintained. Thereby, the thickness is determined by the thickness of the base plate 225, the thickness of the semiconductor die 205, and additionally the displacement required for the leads 210-220. Consequently, the thickness of the package 230 is increased in order to keep the length of the package at a minimum.
The displacement between the semiconductor die 205 and the leads 210-220 may be necessary to ensure a secure and correct position of the semiconductor die 205, the base plate 225 and the leads 210-220 when molding/casting the package 230 of the power electronic module 200.
Further, the bond wires 235 are provided in a curved and not a flat shape. Between different connection points, the bond wires 235 are curved in order to avoid mechanical stress at the connection points of the bond wire 235 during the molding/casting of the package 230. The illustrated SMD package 230 is 4.45 mm thick.
An exemplary embodiment of the second design enabling the power electronic module 300 to combine multiple semiconductor dies is shown in FIG. 11. In particular, FIG. 11 illustrates a top view of the exemplary power electronic module with a semiconductor die mounted on an insulating substrate.
As can be seen from FIG. 11, the semiconductor die 305 is bonded at its back surface with a region of the insulating substrate 315 to form a power electronic module 300. In addition, the insulating substrate 315 and active regions 310 are provided on the substrate of the power electronic module. In order to allow for a secure mounting of the semiconductor die 305 on the insulating substrate 315, the active regions 310 and the semiconductor die 305 have to be spaced at a predefined distance (namely a keep-out area). In particular, the placement of multiple semiconductor dies on a same insulating substrate results in large keep-out areas which cannot be used for active regions.
Another exemplary embodiment of the second design enabling the power electronic module 300 to combine multiple semiconductor dies is shown in FIG. 12. In particular, FIG. 12 illustrates a perspective view of the exemplary power electronic module 300 shown in FIG. 11.
As can be seen from FIG. 12, the semiconductor die 305 is also bonded at its back surface with a region of the insulating substrate 315 to form power electronic module 300. Further, the semiconductor die 305 is also placed at a distance to the active regions 310 in order to maintain a keep-out area around the semiconductor die 305.